The present invention relates to a new and improved apparatus for shaping the edge of a groove in a valve sleeve. In particular, the present invention relates to an apparatus for shaping the edge of a groove formed in the internal surface of a cylindrical valve sleeve. The edge of the groove shaped by the apparatus is defined by the intersection of the internal surface of the valve sleeve and a surface which extends transverse to the axis of the valve sleeve.
A valve assembly for a vehicle power steering apparatus is disclosed in U.S. Pat. No. 4,276,812. The valve assembly includes a valve sleeve and a valve core located within the valve sleeve. The valve core and valve sleeve rotate relatively to control fluid flow through the valve assembly. Flow control grooves are formed in the internal surface of the valve sleeve. The internal flow control grooves have straight edges which extend parallel to the central axis of the valve sleeve. The groove edges are formed by the intersection of surfaces which extend transverse to the axis of the valve sleeve and the internal surface of the valve sleeve. When the valve sleeve and valve core are rotated relatively, fluid flows across the straight edges of the internal flow control grooves.
The flow control grooves in the valve sleeve of U.S. Pat. No. 4,276,812 are formed by an end mill. The end mill is first moved into the interior of the valve sleeve and rotated. The end mill is then moved into the material of the valve sleeve and moved axially of the valve sleeve to cut a groove in the internal surface of the valve sleeve.
Deflection of the milling tool results in the grooves cut in one valve sleeve not being identical to the grooves cut in another valve sleeve. As a result, the flow provided by one valve sleeve is not consistent with the flow provided by another valve sleeve. Thus, if the valve sleeves are used in power steering valves, each power steering valve would provide different steering reactions.